The invention relates to a method for automatically generating smoothed characteristic diagrams for an electronic engine control of a piston-type internal combustion engine.
Modern industrial society views mobility for the transport of goods and the drive to work as playing an important role. A great deal of this movement occurs in the streets, wherein the piston-type internal combustion engine as the driving source plays a dominating role.
Public discussion in recent years has focused on the emissions of piston-type internal combustion engines. The laws reflect this in the form of increasingly lower limit values for emissions. Furthermore, prices for the required types of fuel are on the rise. Together these two factors make it necessary to have piston-type internal combustion engines with lower emissions and less consumption.
To reach this goal, piston-type internal combustion engines must consequently be developed and constructed in accordance with the latest findings. Not only does modern mechanical design play a role in this, but the electronic components are also becoming more and more important because of the enormous increase in options and flexibility.
These days an electronic control device is used in place of the formerly used variable speed governor to adjust the ignition point to the requirements. This control device can consider influencing variables with more precision and can be adapted easier to various applications.
With these control devices, the dependencies between the input variables, for example the speed, and the output variables, meaning the adjustment variables such as advance angle, injected fuel amount etc., are deposited in characteristic diagrams that contain characteristic diagram points for each operating state of a piston-type internal combustion engine. These points predetermine the actual values for the adjustment variables.
During the development of a piston-type internal combustion engine, the necessary characteristic diagrams must be filled with values. Until now, the characteristic diagrams were created by experienced developers on the basis of testing stand measurements, experimental methods and in part also intuition based on measurements from a reference engine. This process required a considerable amount of developmental time and generally did not yield optimum results.
The expenditure for adapting the characteristic diagrams strongly depends on the number of parameters to be calibrated. In the process, the degrees of freedom in control devices increases, for example by introducing the exhaust gas re-circulation (EGR), the camshaft adjustment, a variable intake system, just to mention a few. It is nearly impossible for humans to keep a clear overview of the consequently required solution of a more than three-dimensional optimization task with many parameters.
For that reason, systems for the automatic optimization of characteristic diagrams and the related software were developed, which generated characteristic diagrams based on testing stand measurements and algorithms with a mathematical foundation. Fewer road tests with vehicles are thus needed and an optimization of the piston-type internal combustion engine is possible, even if the complete vehicle is not yet available. On the one hand, this shortens the developmental time and therefore also the xe2x80x9ctime-to-marketxe2x80x9d and consequently saves costs. On the other hand, the generated results are reproducible and do not depend on being optimized by a human being using intuition. The optimization system is furthermore easier to adapt and to adjust to other predetermined data.
Owing to the relatively short time requirement, the automatic optimization with different configurations can be carried out several times. Thus, it is possible to realize several scenarios that could not be realized with reasonable expenditure during a practical experiment.
With the methods used so far, it is possible to create characteristic xe2x80x9cmotherxe2x80x9d diagrams for a given piston-type internal combustion engine design, based on which the corresponding characteristic diagram data carriers can be set up for the later series production and also for the series production of the engine control. However, the disadvantage of the method used so far is that when carrying out the automatic optimization, a value is generated for each support location or each operating point of a characteristic diagram, without taking into account the interrelations between neighboring support locations. This results in jumps in the calibration data for neighboring support locations, which endanger the transferability of the optimization result as well as the drivability during the practical vehicle deployment. Strong jumps in the calibration data of neighboring support locations must therefore be avoided.
In the process, jumps occur during two phases of the optimization. On the one hand, the problem is that the results of making adjustments within a characteristic diagram area that is optimized according to the same criteria show such adjustment variable jumps. On the other hand, there is the problem that jump-type transitions occur when joining characteristic diagram areas that are optimized according to different criteria.
Thus, it is the object of the invention to find a method that avoids strong jumps in the calibration data during the optimization run, but nevertheless permits a good optimization result and makes it possible to generate a smoothed characteristic diagram.
This object is solved with the method steps provided in claim 1. Modifications of the method according to the invention are specified in claims 2 to 4.